Three-dimensional sensors are important for autonomous vehicles, drones, and other applications. They may be used, for example, for obstacle detection in an autonomous or semi-autonomous vehicle. Long range radar has become a common option for high end automobiles due to its low cost and high reliability. While the angular resolution of a millimeter wave radar (e.g., operating at 72 GHz W band) could be better than 2 degrees, such angular resolution is insufficient to guide autonomous vehicles at high speed. For example, a 200 meter sensing range is usually considered to be necessary for cars travelling at 120 km per hour (i.e., about 33 m/s or 75 mph). It may be calculated that an angular resolution of 0.2 degrees or less is necessary to achieve a spatial resolution of 0.7 m for an object at 200 m away. This spatial resolution would ensure the detection of a normal sized vehicle with at least one pixel. On the other hand, current commercially available three-dimensional sensors based on lidars are very expensive compared to the average selling price of a consumer automobile.